1. Field of the Invention
This invention relates to combustion turbine engines with intercooling, recuperation, reheat, saturation, heat recovery steam generation.
2. Background Information
A typical and currently available simple cycle combustion turbine consists of a compressor for compressing the atmospheric air, a combustor for heating the compressed air, a turbine for power production and an electric generator for converting mechanical energy into electrical energy. A more sophisticated combustion turbine concept with a number of compressors with intercoolers and with a number of turbines with associated combustors and, also, with a recuperator, has been theoretically known at least since the 1920's.
Major features of the conventional, generic, sophisticated combustion turbine concept as disclosed in the article entitled "Optimization of Gas Turbine Cycles with Variable Number of Combustion, Compressor and Intercooler Stages", document no. 81-JPGC-CT-6 published in 1981 by the American Society of Mechanical Engineers, are as follows:
The highest pressure turbine with associated combustor has the highest inlet temperature. The lower pressure turbines with associated combustors have the same (as the highest pressure turbine) inlet temperature; PA1 The expansion pressure ratios of all turbines theoretically shall be equal; and PA1 The compression pressure ratios of all compressors theoretically shall be equal. Earlier patents, for example, U.S. Pat. No. 2,584,232 to Sedille utilize this generic theoretical combustion turbine cycle with the aforementioned features. The major thrust of these patents is the utilization of available and otherwise wasted heat resources of the generic theoretical combustion turbine concept for improving the resulting power plant efficiency. These heat resources are used for steam generation and additional electric power production by the bottoming steam turbine or via steam injection. PA1 The inlet temperature to the highest pressure turbine (FIG. 2, point 23), of the plurality of the additional shaft assemblies, has the lowest inlet temperature at the level of current industrial expander technology (1400.degree. F. to 1600.degree. F.). The other turbines (point 13) of the additional shaft assemblies (except the lowest pressure turbine), have approximately the same inlet temperature, or only slightly higher (potentially increasing with reduced inlet pressure). The highest inlet temperature is at the inlet to the lowest pressure turbine (point 3) of the power shaft assembly and presents the current state of the art temperature level for combustion turbines (2300.degree. F. to 2500.degree. F.). This distribution of turbine inlet temperatures is in contrast with the prior art theoretical cycle as disclosed in U.S. Pat. No. 2,584,232 and provides very high thermal cycle efficiency, making practical engineering sense. It addresses the first engineering problem of the prior art: a prohibitive coincidental high pressure and temperature at the high pressure turbine inlet. PA1 Consequently, the reduced inlet temperatures of the high and intermediate pressure turbines (of the additional shaft assemblies), reduce the inlet temperatures to the downstream combustors. This addresses the second engineering problem of the prior art cycle. PA1 The optimized distribution of the expansion pressure ratio among a plurality of turbines results in approximately equal pressure ratios for all turbines (of the additional shaft assemblies), except for the lowest pressure turbine (of the power shaft assembly). The lowest pressure turbine has the highest pressure ratio, corresponding to that of a simple cycle combustion turbine, which components are utilized for the power shaft assembly. This allows the modification of an existing combustion turbine into the inventive concept--the major thrust of this invention. PA1 The optimized distribution of the overall compression pressure ratio among compressors is dictated by considerations of the balanced high and intermediate pressure shafts (of the additional shaft assemblies) and is different from the equal distribution for the prior art cycle. PA1 The recuperator recovers the high temperature exhaust gas heat from the power shaft assembly turbine to preheat the air prior to entering the highest pressure combustor of the additional shaft assemblies.
No current practical applications of this prior art theoretical sophisticated combustion turbine cycle have been established, due to a number of engineering problems facing the power plant designers.
The first and the most important engineering problem is that the highest pressure turbine for the prior art combustion turbine concept has the highest inlet temperature. This presents a serious challenge because of high thermal and transient stresses in the high pressure and temperature turbine components, and requires special materials and engineering yet to be developed.
The second engineering problem is a result of the fact that for a typical prior art concept a plurality of combustion turbines with the same inlet temperatures and equal pressure ratios have very high exhaust gas flow temperatures which are the inlet temperatures for a plurality of downstream combustors. This is yet another serious engineering challenge.